Genetics-based deperturbation analysis for the spin-orbit coupled ${\rm A}^1\Sigma^+$ and ${\rm b}^3\Pi_{0^+}$ states of LiRb

TL;DR

This paper uses genetic algorithms to analyze and fit potential energy curves and spin-orbit coupling in LiRb molecules, enabling prediction of optimal states for molecular state transfer.

Contribution

It introduces a novel genetic algorithm-based deperturbation method for coupled electronic states of LiRb, providing detailed potential energy curves and transition properties.

Findings

Identified suitable intermediate states for Raman transfer to the ground state.

Fitted potential energy curves and spin-orbit coupling parameters from experimental data.

Predicted transition dipole moments for key molecular transitions.

Abstract

We present a deperturbation analysis of the spin-orbit coupled $\rm A^1\Sigma^+$ and $\rm b^3\Pi_{0^+}$ states of LiRb based on the rovibrational energy levels observed previously by photoassociation spectroscopy in bosonic $^7$Li$^{85}$Rb molecule. Using the genetic algorithm, we fit the potential energy curves of the $\rm A^1\Sigma^+$ state and the $\rm b^3\Pi$ state into point-wise form. We then fit these point-wise potentials along with the spin-orbit coupling into expanded Morse oscillator functional form and optimise analytical parameters based on the experimental data. From the fitted results, we calculate the transition dipole moment matrix elements for transitions from the rovibrational levels of the coupled $\rm A^1\Sigma^+$-$\rm b^3\Pi_{0^+}$ state to the Feshbach state and the absolute rovibrational ground state for fermionic $^6$Li$^{87}$Rb molecule. Based on the calculated transition dipole moment matrix elements, several levels of the coupled $\rm A^1\Sigma^+$-$\rm b^3\Pi_{0^+}$ state are predicted to be suitable as the intermediate state for stimulated Raman adiabatic passage transfer from the Feshbach state to the absolute rovibrational ground state. In addition, we also provide a similar estimation for ${\rm B}^1\Pi$-${\rm c}^3\Sigma_1^+$-${\rm b}^3\Pi_1$ state based on available $ab\ initio$ interaction potentials.